1. Field of the Invention
The present invention relates to a telecommunication system adopting Link Aggregation and in particular, a dynamic bandwidth control of user traffic in transmission equipment when a failure occurs in the physical link of the telecommunication system, resulting in a fluctuating number of usable physical links.
2. Description of the Related Art
Link Aggregation, which is a technique for utilizing a plurality of physical links as one logical link, is standardized as IEEE802.3ad. For instance, Link Aggregation makes it possible to bundle eight physical links having 1-Gbps bandwidth for use as an 8-Gbps logical link. As such, Link Aggregation provides a benefit of increasing bandwidth without using high speed physical links. And if failure occurs in some of the physical links, the entirety of the link is operable instead of being interrupted as long as at least one physical link is usable. Therefore the adoption of Link Aggregation enables the implementation of a failure resistant telecommunication system. In the following description, a logical link per se integrated by Link Aggregation is referred to as Link Aggregation or simply LA.
Referring to FIG. 1, let a situation when a failure occurs in a physical link within transmission equipment used for a telecommunication system adopting Link Aggregation be described.
As shown by FIG. 1 conceptually, let it be assumed that users A and B are using a 4.0 Gbps Link Aggregation integrating four ports of physical links, each of which is connected to a 1.0 Gbps port, and that each output data of the users A and B is being shaped. Let it also be assumed that for user A, an input rate of 2.0 Gbps, and for output, a shaping rate of 2.0 Gbps and an actual output rate of 2.0 Gbps is in effect; and for the user B, an input rate of 2.0 Gbps, and for output, a shaping rate of 2.0 Gbps and an actual output rate of 2.0 Gbps is in effect.
In this configuration, if failures occur in two ports out of the four ports as shown by FIG. 1, through Link Aggregation reconfiguration, the number of integrated physical links changes from four to two, resulting in the maximum bandwidth of the Link Aggregation becoming 2.0 Gbps. As such, the maximum bandwidth of the Link Aggregation changes dynamically depending on the failure condition of the respective physical links which are integrated.
A setup value of bandwidth control such as shaping, however, is usually established with an assumption of no failure occurrence in the integrated respective physical links, the pre-established bandwidth control becomes meaningless if a failure occurs in the physical link lowering the maximum bandwidth below the shaping rate.
Because of the above, the bandwidth of the reconfigurated Link Aggregation is occupied by the traffic for the user A, allowing no flow of data signal for the user B in an extreme case, as shown by FIG. 1.
With regard to the above described problem, let Link Aggregation reconfiguration in the case of a failure occurrence in a physical link of conventional transmission equipment be described, while referring to FIGS. 2 and 3.
FIG. 2 illustrates a hardware unit 100 which houses a physical link of transmission equipment and a firmware unit 90 for controlling the hardware unit 100. The firmware unit 90 comprises an external command receiving unit 91, an external command process unit 92, a bandwidth control unit 93, a bandwidth control information setup retention unit 94, a hardware control unit 95, a link failure detection unit 96, an LA reconfiguration control unit 97 and an event notification unit 98.
Note that the terms “bandwidth control setup” and “bandwidth control information setup” are used in the following descriptions, where “bandwidth control setup” means to set a specific setup value, such as a shaping rate “2.0 Gbps” for the user A, as exemplified by FIG. 1, individually in the hardware unit 100, while “bandwidth control information setup” means to set a setup value used for the “bandwidth control setup” in the bandwidth control information setup retention unit 94. The above noted definitions also apply to a later noted description of the present invention.
For instance, as an external command such as a command for a bandwidth control information setup per user is issued, the command is received by the external command receiving unit 91, interpreted by the external command process unit 92, provided to the bandwidth control unit 93, followed by the bandwidth control information setup retention unit 94 setting the bandwidth control information per user to be retained thereby. The bandwidth control unit 93 reads out the bandwidth control information per user retained by the bandwidth control information setup retention unit 94 and instructs the hardware control unit 95 to set a bandwidth control. The hardware control unit 95 sets the instructed bandwidth control setup in the hardware unit 100 and has it execute a bandwidth control per user.
FIG. 3 shows a conventional Link Aggregation reconfiguration flow in the case of a failure occurrence in a physical link.
As a failure occurs in an accommodated physical link, the hardware unit 100 issues an interrupt due to the occurrence of link failure in accordance with some cause and the link failure detection unit 96 receives it. This constitutes a judgment of a link failure cause occurrence becoming “yes” (the step S101 noted in FIG. 3) (simply “S101” hereinafter), so that the link failure detection unit 96 detects failure in units of physical links to judge whether or not an LA reconfiguration cause has occurred (S102).
If the judgment for S102 is “yes”, the link failure detection unit 96 notifies the LA reconfiguration control unit 97 of a LA reconfiguration cause occurrence (S103).
The LA reconfiguration control unit 97 instructs the hardware control unit 95 to reconfigurate LA (S104) and the hardware control unit 95 carries out a LA reconfiguration control for the hardware unit 100 (S105).
Meanwhile, the LA reconfiguration control unit 97 notifies maintenance personnel of an LA reconfiguration event by way of the event notification unit 98 (S106).
As described above, coordination between a link reconfiguration control and bandwidth control has not been performed in the conventional method. Because of this, it is possible for a state to occur where user A traffic occupies all the bandwidth resulting in user B′ data signal not flowing. As such, there have been cases where unfairness occur in the allotment of usable bandwidth among respective users such as the traffic of a specific user among equal priority users using all the bandwidth, resulting in the traffic of other users being unable to pass through.
A below noted patent document 1 discloses bulk transmission equipment for carrying out bulk communication by using a plurality of links as with the Link Aggregation. The patent document 1 discloses a technique for carrying out bulk communication only on the normal links if a failure occurs in one link of the plurality thereof during bulk communication, while a method of preventing the possibility of an unfair state in usable bandwidth occurring among the respective users is not noted.
[Patent document 1] Japanese Published Patent Application No. 2001-136234